Solid state lighting devices with accessible electrodes and methods of manufacturing

ABSTRACT

Various embodiments of light emitting dies and solid state lighting (“SSL”) devices with light emitting dies, assemblies, and methods of manufacturing are described herein. In one embodiment, a light emitting die includes an SSL structure configured to emit light in response to an applied electrical voltage, a first electrode carried by the SSL structure, and a second electrode spaced apart from the first electrode of the SSL structure. The first and second electrode are configured to receive the applied electrical voltage. Both the first and second electrodes are accessible from the same side of the SSL structure via wirebonding.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.16/377,871, filed Apr. 8, 2019, which is a continuation of U.S.application Ser. No. 15/961,473, filed Apr. 24, 2018, now U.S. Pat. No.10,256,369; which is a continuation of U.S. application Ser. No.15/262,956, filed Sep. 12, 2016, now U.S. Pat. No. 9,985,183; which is acontinuation of U.S. application Ser. No. 14/614,247, filed Feb. 4,2015, now U.S. Pat. No. 9,444,014; which is a continuation of U.S.application Ser. No. 13/926,799, filed Jun. 25, 2013, now U.S. Pat. No.9,000,456; which is a continuation of U.S. application Ser. No.12/970,726, filed Dec. 16, 2010, now U.S. Pat. No. 8,476,649; each ofwhich is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure is related to light emitting dies (e.g., lightemitting diodes (“LEDs”)) and solid state lighting (“SSL”) devices withlight emitting dies having accessible electrodes and methods ofmanufacturing.

BACKGROUND

SSL devices can have light emitting dies with different electrodeconfigurations. For example, FIG. 1A is a cross-sectional view of alight emitting die 10 with lateral electrodes. As shown in FIG. 1A, thelight emitting die 10 includes a substrate 12 carrying an LED structure11 comprised of N-type gallium nitride (GaN) 14, GaN/indium galliumnitride (InGaN) multiple quantum wells (“MQWs”) 16, and P-type GaN 18.The light emitting die 10 also includes a first electrode 20 on theN-type GaN 14 and a second electrode 22 on the P-type GaN 18. As shownin FIG. 1A, the first and second electrodes 20 and 22 are both on thefront side of the LED structure 11 and readily accessible.

FIG. 1B shows a light emitting die 10′ with vertical electrodes. Thelight emitting die 10′ includes a first electrode 20 on the N-type GaN14 and second electrode 22 under the P-type GaN 18. The light emittingdie 10′ can have higher degrees of current spreading between the firstand second electrodes 20 and 22 than the light emitting die 10 of FIG.1A. However, the second electrode 22 is not readily accessible becauseit is buried between the P-type GaN 18 and the substrate 12. Inaddition, the first electrode 20 partially blocks the generated light(as indicated by the arrow 15 a), and thus only allows a portion of thegenerated light to be extracted (as indicated by the arrow 15 b). Thus,the light extraction efficiency of the light emitting die 10′ may belimited.

One approach for improving the light extraction efficiency of lightemitting dies with vertical electrodes is by incorporating a “buried”electrode. As shown in FIG. 1C, an light emitting die 10″ includes anopening 21 extending into the N-type GaN 14 from the substrate 12. Aninsulating material 25 lines the sidewalls 23 of the opening 21. Aconductive material is disposed in the opening 21 to form the firstelectrode 20. The light emitting die 10″ with the buried first electrode20 can have improved light extraction efficiencies because it does notcover any portion of the N-type GaN 14. However, neither of the firstand second electrodes 20 and 22 are readily accessible in this design,and they require precise alignment with external conductors to avoidelectrode mismatch. Accordingly, several improvements in electrodeconfiguration of light emitting dies may be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional diagram of a light emitting diewith lateral electrodes in accordance with the prior art.

FIG. 1B is a schematic cross-sectional diagram of a light emitting diewith vertical electrodes in accordance with the prior art.

FIG. 1C is a schematic cross-sectional diagram of a light emitting diewith a buried electrode in accordance with the prior art.

FIG. 2A is a schematic cross-sectional diagram of a light emitting diewith vertical electrodes in accordance with embodiments of the presenttechnology.

FIG. 2B is a schematic top plan view of the light emitting die shown inFIG. 2A.

FIG. 3A is a schematic cross-sectional diagram of a light emitting diewith a buried electrode in accordance with embodiments of the presenttechnology.

FIG. 3B is a schematic top plan view of the light emitting die shown inFIG. 3A.

FIG. 4 is a schematic illustration of an SSL device incorporating thelight emitting dies of FIGS. 2A-3B in accordance with embodiments of thepresent technology.

FIG. 5A is a schematic cross-sectional diagram of a light emitting diewith a buried electrode in accordance with embodiments of the presenttechnology.

FIG. 5B is a schematic top plan view of the light emitting die shown inFIG. 5A.

FIG. 5C is a schematic cross-sectional diagram of a light emitting diewith a buried electrode in accordance with embodiments of the presenttechnology.

FIG. 6A is a schematic cross-sectional diagram of a light emitting diewith a buried electrode in accordance with additional embodiments of thepresent technology.

FIG. 6B is a schematic top plan view of the light emitting die shown inFIG. 6A.

DETAILED DESCRIPTION

Various embodiments of light emitting dies, SSL devices with lightemitting dies, and methods of manufacturing are described below. As usedhereinafter, the term “SSL device” generally refers to devices with oneor more solid state light emitting dies, such as LEDs, laser diodes(“LDs”), and/or other suitable sources of illumination other thanelectrical filaments, a plasma, or a gas. A person skilled in therelevant art will also understand that the technology may haveadditional embodiments, and that the technology may be practiced withoutseveral of the details of the embodiments described below with referenceto FIGS. 2A-6B.

FIG. 2A is a schematic cross-sectional diagram of a light emitting die100, and FIG. 2B is a top plan view of the light emitting die 100 shownin FIG. 2A. As shown in FIG. 2A, the light emitting die 100 can includean SSL structure 111, a first electrode 120, a second electrode 122, anda substrate 102 carrying the SSL structure 111 with an insulatingmaterial 103 therebetween. Only certain components of the light emittingdie 100 are shown in FIGS. 2A and 2B, and it will be appreciated thatthe light emitting die 100 can also include a lens, a mirror, and/orother suitable optical and/or electrical components in otherembodiments.

In one embodiment, the substrate 102 can include a metal, a metal alloy,a doped silicon, and/or other electrically conductive substratematerials. For example, in one embodiment, the substrate 102 can includecopper, aluminum, and/or other suitable metals. In other embodiments,the substrate 102 can also include a ceramic material, a silicon, apolysilicon, and/or other generally non-conductive substrate materials.For example, the substrate 102 can include intrinsic silicon and/orpolysilicon materials. Even though only one SSL structure 111 is shownon the substrate 102, two, three, or any other desired number of SSLstructure 111 may be formed on the substrate 102 in practice.

In certain embodiments, the insulating material 103 can include siliconoxide (SiO₂), silicon nitride (Si₃N₄), and/or other suitablenon-conductive materials formed on the substrate 102 via thermaloxidation, chemical vapor deposition (“CVD”), atomic layer deposition(“ALD”), and/or other suitable techniques. In other embodiments, theinsulating material 103 can include a polymer (e.g.,polytetrafluoroethylene and/or other fluoropolymer oftetrafluoroethylene), an epoxy, and/or other polymeric materials. In oneexample, the polymeric materials may be configured as a preformed sheetor tape that can be attached to the substrate 102 via solid-solidbonding, adhesives, and/or other suitable techniques. In anotherexample, the polymeric materials may be configured as a paste or aliquid that may be applied to the substrate 102 and subsequently cured.In further embodiments, the insulating material 103 may be omitted ifthe substrate 102 is electrically insulative.

The SSL structure 111 is configured to emit light and/or other types ofelectromagnetic radiation in response to an applied electrical voltage.In the illustrated embodiment, the SSL structure 111 includes a firstsemiconductor material 104 having a first surface 113 a proximate afirst side 111 a of the light emitting die 100, an active region 106,and a second semiconductor material 108 having a second surface 113 bproximate a second side 111 b of the light emitting die 100. The SSLstructure 111 has a stack thickness equal to the sum of the thicknessesof the first semiconductor material 104, the active region 106, and thesecond semiconductor material 108. The stack thickness of the SSLstructure 111 shown in FIG. 2A, for example, is the distance between thefirst surface 113 a and the second surface 113 b. In other embodiments,the SSL structure 111 can also include silicon nitride, aluminum nitride(AlN), and/or other suitable intermediate materials.

In certain embodiments, the first semiconductor material 104 can includeN-type GaN (e.g., doped with silicon (Si)), and the second semiconductormaterial 108 can include P-type GaN (e.g., doped with magnesium (Mg)).In other embodiments, the first semiconductor material 104 can includeP-type GaN, and the second semiconductor material 108 can include N-typeGaN. In further embodiments, the first and second semiconductormaterials 104 and 108 can individually include at least one of galliumarsenide (GaAs), aluminum gallium arsenide (AlGaAs), gallium arsenidephosphide (GaAsP), gallium(III) phosphide (GaP), zinc selenide (ZnSe),boron nitride (BN), AlGaN, and/or other suitable semiconductormaterials.

The active region 106 can include a single quantum well (“SQW”), MQWs,and/or a bulk semiconductor material. As used hereinafter, a “bulksemiconductor material” generally refers to a single grain semiconductormaterial (e.g., InGaN) with a thickness greater than about 10 nanometersand up to about 500 nanometers. In certain embodiments, the activeregion 106 can include an InGaN SQW, GaN/InGaN MQWs, and/or an InGaNbulk material. In other embodiments, the active region 106 can includealuminum gallium indium phosphide (AGaInP), aluminum gallium indiumnitride (AlGaInN), and/or other suitable materials or configurations.

In certain embodiments, at least one of the first semiconductor material104, the active region 106, and the second semiconductor material 108can be formed on the substrate material 102 via metal organic chemicalvapor deposition (“MOCVD”), molecular beam epitaxy (“MBE”), liquid phaseepitaxy (“LPE”), and hydride vapor phase epitaxy (“HVPE”). In otherembodiments, at least one of the foregoing components and/or othersuitable components (not shown) of the SSL structure 111 may be formedvia other suitable epitaxial growth techniques.

As shown in FIGS. 2A and 2B, the first electrode 120 is spaced apartfrom the second electrode 122 by the vertical thickness of the entireSSL structure 111. The shortest distance between the first and secondelectrodes in this embodiment, therefore, is the distance from the firstsurface 113 a to the second surface 113 b. In the illustratedembodiment, the first electrode 120 includes a plurality of electrodefingers 121 (three are shown for illustration purposes) coupled to oneanother by a cross member 123. The electrode fingers 121 extendgenerally parallel to an axis 105 (FIG. 2B) of the SSL structure 111,and the cross member 123 is generally perpendicular to the electrodefingers 121. In certain embodiments, the electrode fingers 121 and/orthe cross member 123 can include indium tin oxide (“ITO”), aluminum zincoxide (“AZO”), fluorine-doped tin oxide (“FTO”), and/or other suitabletransparent conductive oxides (“TCOs”). In other embodiments, theelectrode fingers 121 and/or the cross member 123 can include copper(Cu), aluminum (A), silver (Ag), gold (Au), platinum (Pt), and/or othersuitable metals. In further embodiments, the electrode fingers 121and/or the cross member 123 can include a combination of TCOs and one ormore metals. Techniques for forming the electrode fingers 121 and/or thecross member 123 can include MOCVD, MBE, spray pyrolysis, pulsed laserdeposition, sputtering, electroplating, and/or other suitable depositiontechniques.

The second electrode 122 can include a reflective and conductivematerial (e.g., silver or aluminum), at least a portion of which can beexposed through the SSL structure 111. For example, as shown in FIGS. 2Aand 2B, the second electrode 122 includes a covered first portion 122 aand an exposed second portion 122 b laterally extending beyond the SSLstructure 111. As a result, the exposed second portion 122 b can form aconnection site 126 for interconnecting with external components (notshown) via a wirebond and/or other suitable couplers.

During manufacturing, in certain embodiments, the substrate 102 may beselected to have a first lateral dimension L_(S) greater than a secondlateral dimension L_(D) of the SSL structure 111. The insulatingmaterial 103 and the second electrode 122 (e.g., aluminum, silver, orother reflective and conductive materials) can then be formed on thesubstrate 102 in sequence. In one embodiment, the SSL structure 111 maybe attached to the second electrode 122 on the substrate 102 viasolid-solid bonding (e.g., copper-copper bonding, nickel-tin bonding,and gold-tin bonding) between the second electrode 122 and the secondsemiconductor material 108. In another embodiment, a bonding material(e.g., gold-tin, not shown) may be formed on the second semiconductormaterial 108. In yet another embodiment, a reflective material (e.g.,silver, not shown) may be formed on the second semiconductor material108 before forming the bonding material. The SSL structure 111 can thenbe bonded to the substrate 102 via solid-solid bonding between thesecond electrode 122 and the bonding material. In further embodiments,the SSL structure 111 may be attached to the substrate 102 via othersuitable mechanisms.

In other embodiments, the substrate 102 may be selected to have a firstlateral dimension L_(S) that is generally the same as the lateraldimension L_(D) of the SSL structure 111. After attaching the SSLstructure 111 to the substrate 102, a portion of the SSL structure 111may be removed to form the exposed second portion 122 b of the secondelectrode 122. Techniques for removing a portion of the SSL structure111 can include partial dicing (e.g., with a die saw), laser ablation,wet etching, dry etching, and/or other suitable technique. In furtherembodiments, the partially exposed second electrode 122 may be formedvia other suitable techniques.

Several embodiments of the light emitting die 100 can have theconnection accessibility of the light emitting die 10 of FIG. 1A withcurrent spreading characteristics generally similar to that of the lightemitting die 10′ of FIG. 1B. As shown in FIGS. 2A and 2B, the exposedsecond portion 122 b of the second electrode 122 provides ready accessfor external connection. As a result, both the first electrode 120 andthe second electrode 122 can be accessed from the same side (i.e., thefirst side 111 a) of the SSL structure 111. Meanwhile, the covered firstportion 122 a of the second electrode 122 is arranged vertically acrossthe SSL structure 111 with respect to the first electrode 120, and thusproviding better current distribution through the SSL structure 111compared to the lateral device in FIG. 1A. As a result, severalembodiments of the light emitting die 100 can operate with highefficiency while providing the connection accessibility of the lightemitting die 10 of FIG. 1A.

Even though the exposed second portion 122 b of the second electrode 122is shown in FIG. 2B as extending substantially the entire depth D (FIG.2B) of the SSL structure 111 along the axis 105, in other embodimentsthe second portion 122 b may extend only partially along the axis 105 ofthe SSL structure 111. For example, as shown in FIGS. 3A and 3B, thesecond portion 122 b may be exposed through a notch 128 in the SSLstructure 111 formed on the substrate 102 with the insulating material103. The notch 128 has a depth d (FIG. 3B) that is less than the depth D(FIG. 2B) of the SSL structure 111. In other embodiments, the secondportion 122 b may also include a plurality of individual sections spacedapart from one another. For example, three sections (identifiedindividually as first, second, and third sections 122 b, 122 b′, and 122b″) are shown in FIG. 3B for illustration purposes. Each of the threesections 122 b, 122 b′, and 122 b″ may form a connection site 126 forconnecting to an external component (not shown). As a result, the lightemitting die 100 can provide a plurality of connection sites 126 toreceive/transmit signals and/or power to/from more than one component.In further embodiments, the insulating material 103 may be omitted fromthe light emitting die 100.

Several embodiments of the light emitting die 100 can be packaged in anSSL device with improved thermal dissipation characteristics overconventional devices. For example, FIG. 4 is a schematic illustration ofan SSL device 150 incorporating the light emitting dies 100 of FIGS.2A-3B in accordance with embodiments of the present technology. As shownin FIG. 4, the SSL device 150 can include a carrier 152 carrying aplurality of light emitting dies 100. Four light emitting dies 100 areshown in FIG. 4 for illustration purposes. In other embodiments, the SSLdevice 150 can include any other desired number of light emitting dies100.

The carrier 152 can include a metal, a metal alloy, and/or other typesof thermally conductively structure. The SSL assembly 150 can alsoinclude a first terminal 154 laterally spaced apart from a secondterminal 156 on the carrier 152. The first and second terminals 154 and156 are formed on insulative pads 155 and 157, respectively. Theinsulative pads 155 and 157 can include silicon oxide, silicon nitride,and/or other suitable types of electrically insulative materials.

As shown in FIG. 4, the first terminal 154, the plurality of lightemitting dies 100, and the second terminal 156 are electrically coupledwith wirebonds 158 in series because the first and second electrodes 120and 122 are both on the front side of the individual light emitting dies100. As a result, the back side of the light emitting dies 100 candirectly contact the surface 152 a of the carrier 152. In operation,such direct contact allows the light emitting dies 100 to readilytransfer heat to the thermally conductive carrier 152, and thusefficiently dissipate heat away from the light emitting dies 100.

FIG. 5A is a schematic cross-sectional diagram of an light emitting die200 with a buried electrode in accordance with another embodiment of thetechnology, and FIG. 5B is a top plan view of the light emitting die 200in FIG. 5A. The light emitting die 200 can include components that aregenerally similar in structure and function as those of the lightemitting die 100 in FIGS. 2A-3B. For example, the light emitting die 200can include the substrate 102 carrying the SSL structure 111 and theexposed second electrode 122 that are generally similar to thosediscussed above with reference to FIGS. 2A-3B. As such, common acts andstructures are identified by the same reference numbers, and onlysignificant differences in operation and structure are described below.

As shown in FIG. 5A, the SSL structure 111 includes a plurality ofopenings 130 (only one is shown in FIG. 5A after it has been filled forclarity) extending from the second electrode 122 into the firstsemiconductor material 104 of the SSL structure 111. A passivationmaterial 125 (e.g., silicon oxide or silicon nitride) has a firstportion 125 a in the opening 130 and a second portion 125 b external tothe opening 130. The first portion 125 a generally conforms to thesidewall 131 of the opening 130 and forms a dielectric liner. The secondportion 125 b has a first surface 127 a in contact with the secondelectrode 122 and a second surface 127 b in contact with the substrate102.

The first electrode 120 can include a conductive material 132 adjacentthe passivation material 125 in the opening 130. In the illustratedembodiment, the conductive material 132 has a first end 132 a that isgenerally co-planar with the passivation material 125 such that thefirst end 132 a of the conductive material 132 is in direct contact withthe substrate 102. The conductive material 132 also includes a secondend 132 b in contact with the first semiconductor material 104. As aresult, the conductive material 132 electrically couples the firstsemiconductor material 104 to the substrate 102.

Several embodiments of the light emitting die 200 can have moreaccessible electrical connections than conventional buried electrodedevices. For example, as shown in FIG. 5A, the first electrode 120 iselectrically coupled to the substrate 102. As a result, in certainembodiments, the substrate 102 may be electrically conductive and usedas a connection site/path to electrically couple external components(not shown). Thus, precise alignment with external conductors may beavoided to reduce production complexity and costs.

In other embodiments, the substrate 102 may be electrically insulativeand may include signal routing components (e.g., metal routing layers134) that route the individual first electrodes 120 to respectivelyelectrical couplers 136 (e.g., solder bumps, solder balls, and/or pillarbumps), as shown in FIG. 5C. In further embodiments, the substrate 102may be partially electrical conductive and partially electricallyinsulative. In yet further embodiments, the light emitting die 200 mayinclude other suitable configurations, as discussed in more detail belowwith reference to FIGS. 6A and 6B.

FIG. 6A is a schematic cross-sectional diagram of a light emitting die300 with a buried electrode, and FIG. 6B is a schematic top plan view ofthe light emitting die 300 shown in FIG. 6A. As shown in FIG. 6A, thelight emitting die 300 includes the substrate 102, the insulatingmaterial 103 on the substrate 102, and the SSL structure 111 withexposed first and second electrodes 120 and 122. The second electrode122 can be generally similar to that discussed above with reference toFIG. 5A. In other embodiments, the insulating material 103 may beomitted.

The first electrode 120 includes the conductive material 132. A firstpart 133 a of the conductive material 132 is adjacent the passivationmaterial 125 in the opening 130. A second part 133 b of the conductivematerial 132 is external to the opening 130. In the illustratedembodiment, a portion of the second part 133 b laterally extends beyondthe second portion 125 b of the passivation material 125 and the secondportion 122 b of the second electrode 122. As a result, the second part133 b of the conductive material 132 (generally designated as connectionarea 135) is at least partially exposed through the SSL structure 111.In other embodiments, the second portion 122 b of the second electrode122 may be laterally opposite and/or having other arrangements relativeto the connection area 135. In further embodiments, the conductivematerial 132 may include a stack of a plurality of conductive materials(not shown). As shown in FIG. 6B, both the first and second electrodes120 and 122 are accessible from the same side of the SSL structure 111.

Even though the light emitting dies 200 and 300 shown in FIGS. 5B and 6Binclude first and/or second electrodes 120 and 122 extending the entiredepth D of the substrate 102, in other embodiments, the first and/orsecond electrodes 120 and 122 may also extend a partial depth D of thesubstrate 102, generally similar to the light emitting die 100 discussedabove with reference to FIG. 3B. In further embodiments, the firstand/or second electrodes 120 and 122 may include a plurality ofelectrode elements (not shown).

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. In addition, many of the elements of one embodiment may becombined with other embodiments in addition to or in lieu of theelements of the other embodiments. Accordingly, the disclosure is notlimited except as by the appended claims.

1. (canceled)
 2. A light emitting die, comprising: a solid statelighting structure including a first semiconductor material, a secondsemiconductor material, and an active region between the first andsecond semiconductor materials; a first electrode disposed on a surfaceof the first semiconductor material opposite the active region; and asecond electrode extending through the first semiconductor material andthe active region and having an end surface contacting the secondsemiconductor material.
 3. The light emitting die of claim 2, wherein aportion of the first electrode extends laterally beyond an edge of thesolid state lighting structure.
 4. The light emitting die of claim 2,wherein a portion of the second electrode extends laterally beyond anedge of the solid state lighting structure.
 5. The light emitting die ofclaim 2, wherein the second electrode is insulated from electricalcontact with the first semiconductor material and the active region by apassivation material.
 6. The light emitting die of claim 5, wherein thepassivation material includes a first region lining a sidewall of afirst portion of the second electrode extending through the firstsemiconductor material and the activate region, and a second regionextending over a surface of the first electrode opposite the firstsemiconductor material.
 7. The light emitting die of claim 2, whereinboth the first electrode and the second electrode are accessible fromthe same side of the light emitting die.
 8. The light emitting die ofclaim 2, wherein both the first electrode and the second electrode areaccessible from opposite sides of the light emitting die.
 9. The lightemitting die of claim 2, further including a substrate, wherein thefirst semiconductor material is between the substrate and the firstelectrode.
 10. The light emitting die of claim 2, further including aconductive substrate, wherein the first semiconductor material isbetween the conductive substrate and the first electrode.
 11. The lightemitting die of claim 2, further including a substrate and an insulatingmaterial on the substrate, wherein the insulating material is betweenthe substrate and the second semiconductor material.
 12. The lightemitting die of claim 2, further including a reflective materialadjacent the second surface of the second semiconductor material. 13.The light emitting die of claim 2, further including a substrate and areflective material between the substrate and the second semiconductormaterial.
 14. The light emitting die of claim 2, wherein the end surfaceof the second electrode contacts the second semiconductor materialpartway through a thickness of the second semiconductor material.
 15. Alight emitting die, comprising: a solid state lighting structureincluding a first semiconductor material, a second semiconductormaterial, and an active region between the first and secondsemiconductor materials; a first electrode disposed on a surface of thefirst semiconductor material opposite the active region; and a secondelectrode extending through the first semiconductor material and theactive region and contacting a region of the second semiconductormaterial located partway through a thickness of the second semiconductormaterial.
 16. The light emitting die of claim 15, wherein a portion ofthe first electrode extends laterally beyond an edge of the solid statelighting structure.
 17. The light emitting die of claim 15, wherein thesecond electrode is insulated from electrical contact with the firstsemiconductor material and the active region by a passivation material.18. The light emitting die of claim 15, further including a substrate,wherein the first semiconductor material is between the substrate andthe first electrode.
 19. The light emitting die of claim 15, furtherincluding a conductive substrate, wherein the first semiconductormaterial is between the conductive substrate and the first electrode.20. The light emitting die of claim 15, further including a reflectivematerial adjacent the second surface of the second semiconductormaterial.
 21. A light emitting die, comprising: a solid state lightingstructure including a first semiconductor material, a secondsemiconductor material, and an active region between the first andsecond semiconductor materials; a first electrode disposed on a surfaceof the first semiconductor material opposite the active region; and asecond electrode extending through the first electrode, the firstsemiconductor material and the active region and having an end surfacein contact with a region of the second semiconductor material locatedpartway through a thickness of the second semiconductor material.